One example of a refrigeration cycle of a prior art air conditioning device is illustrated in FIG. 5. In the refrigeration cycle 1 illustrated in FIG. 5, refrigerant compressed via a compressor 4 driven by a drive source 2 such as a motor is sent to a condenser 5, and air is blown from a fan 12 toward the condenser 5, by which the refrigerant is liquefied. The refrigerant liquefied in the condenser 5 is stored in a receiver 6, the liquid refrigerant from the receiver 6 passes through an expansion valve 10 for controlling the amount of refrigerant passing therethrough to be sent to an evaporator 8, and the refrigerant vaporized in the evaporator 8 is returned to the compressor 4, by which a refrigeration cycle is formed. The expansion valve 10 has a temperature sensor 10a for sensing the refrigerant temperature at the outlet side of the evaporator 8 and a pressure equalizing pipe arrangement 10b for a diaphragm disposed in the expansion valve 10, wherein these values are sent to the expansion valve 10 as feedback, based on which the valve opening is controlled.
FIG. 6 is a vertical cross-sectional view showing an outline of an example of the expansion valve used in the refrigerant cycle illustrated in FIG. 5. The valve body 30 of the expansion valve 10 includes a first passage 32 for introducing gas-liquid two-phase refrigerant formed at a portion between the refrigerant outlet of the condenser 5 and the area headed via the receiver 6 toward the refrigerant inlet of the evaporator 8, and a second passage 34 formed at a portion between the refrigerant outlet of the evaporator 8 and the area headed toward the refrigerant inlet of the compressor 4, which are disposed in a vertically spaced-apart manner constituting a refrigerant pipe line 11 of the refrigeration cycle. The first passage 32 includes a valve hole 32a for decompressing the liquid-phase refrigerant supplied from the refrigerant outlet of the receiver 6 formed along a center line in the longitudinal direction of the valve body 30. A valve seat is formed at the inlet of the valve hole 32a, and the valve member 32b is biased via a biasing means 32c such as a compression coil spring toward the valve seat.
The expansion valve 10 includes an inlet port 321 and a valve chamber 35 communicated with the inlet port 321. The valve chamber 35 is a chamber having a bottom formed coaxially with the center line of the valve hole 32a, which is airtightly sealed via a plug 37. The second passage 34 has ports 341 and 342 connected to the refrigerant pipe line 11.
A valve member driver 36 for driving the valve member 32b is attached to the upper end of the valve body 30. The valve member driver 36 comprises a pressure operation housing 36d having the inner space thereof divided into upper-sectioned and lower-sectioned pressure operation chambers 36b and 36c via a diaphragm 36a. The lower-sectioned pressure operation chamber 36c within the pressure operation housing 36d is communicated with the second passage 34 via a pressure equalizing hole 36e formed concentrically with the center line of the valve hole 32a, so the pressure of the refrigerant vapor within the second passage 34 is loaded on the lower-sectioned pressure operation chamber 36c. 
The pressure equalizing hole 36e has a valve member drive rod 36f concentrically arranged therein, extending from the lower side of the diaphragm 36a to the valve hole 32a of the first passage 32. The valve member drive rod 36f is supported in a vertically slidable manner on a partition wall separating the first and second passages 32 and 34 of the valve body 30, and the lower end thereof is in contact with the valve member 32b. A sealing member 36g for preventing leakage of the refrigerant between the passages 32 and 34 is attached to the outer circumference of the valve member drive rod 36f capable of moving in sliding motion with respect to the partition wall.
A known diaphragm drive fluid is filled in the upper-sectioned pressure operation chamber 36b of the pressure operation housing 36d, and the heat of the refrigerant vapor from the refrigerant outlet of the evaporator 8 flowing through the second passage 34 is transmitted to the diaphragm drive fluid via the valve member drive rod 36f exposed to the second passage 34 and the pressure equalizing hole 36e, and the diaphragm 36a. 
The diaphragm drive fluid within the upper-sectioned pressure operation chamber 36b is gasified in response to the transmitted heat, and the gas pressure thereof is loaded on the upper side of the diaphragm 36a. The diaphragm 36a is moved up and down in response to the difference between the gas pressure and the pressure loaded on the lower side of the diaphragm 36a, and the vertical displacement of the diaphragm is transmitted via the valve member drive rod 36f to the valve member 32b. The flow rate of the refrigerant passing through the valve hole 32a can be controlled via the movement of the valve member 32b moving close to or away from the valve seat of the valve hole 32a. 
FIG. 7 is a view showing the expansion valve illustrated in FIG. 6 from the side having the port 321. As shown in FIG. 7, the prior art expansion valve has a valve body 30 comprising a relatively wide body upper portion 60, a relatively narrow body lower portion 61, and a connecting portion 62 in which the width is continuously narrowed from the width of the body upper portion 30 to the width of the body lower portion 61. According to the valve body 30, the bolt holes 63 and 63 are formed by performing a hole forming process such as a drilling process or a cutting process to the area across the body upper portion 60 and the connecting portion 62.
[Patent document 1] Japanese Patent No. 3545847